In a fluidized bed gasification furnace of a twin tower gasification furnace, a high-temperature bed material (silica sand, limestone, or the like) is fluidized using water vapor injected from a bottom portion so as to form a fluidized bed, and solid raw materials, such as coal, biomass, and the like, are supplied to a free board above the fluidized bed in the above state. The solid raw materials are thermally decomposed using combustible gasification gas (H2, CO, a hydrocarbon) of the solid raw materials and not-yet-combusted solid contents, some of the not-yet-combusted solid contents causes an aqueous gasification reaction with water vapor or moisture vaporized from the solid raw materials so as to generate combustible gasification gas (H2 and CO), and some of CO reacts with water vapor, thereby generating CO2 and H2O.
An apparatus for supplying solid raw materials to the fluidized bed gasification furnace is disclosed in, for example, Patent Document 1. In the raw material supplying apparatus, solid raw materials are supplied using a screw feeder to the inside of a fluidized bed formed in the fluidized bed gasification furnace, and the solid raw materials are brought into sufficient contact with a high-temperature bed material and water vapor.